Electronic devices comprising active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes, organic photovoltaic devices, organic photosensors, organic transistors and memory array devices. Devices comprising organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.
A typical organic light-emissive device (“OLED”) is fabricated on a glass or plastic substrate coated with a transparent anode such as indium-tin-oxide (“ITO”). A layer of a thin film of at least one electroluminescent organic material is provided over the first electrode. Finally, a cathode is provided over the layer of electroluminescent organic material. Charge transporting, charge injecting or charge blocking layers may be provided between the anode and the light-emitting layer and/or between the cathode and the light-emitting layer.
In operation, holes are injected into the device through the anode and electrons are injected into the device through the cathode. The holes and electrons combine in the organic light-emitting layer to form excitons which then undergo radiative decay to give light.
In WO90/13148 the organic light-emissive material is a conjugated polymer such as poly(phenylenevinylene). In U.S. Pat. No. 4,539,507 the organic light-emissive material is of the class known as small molecule materials, such as tris-(8-hydroxyquinoline) aluminium (“Alq3”).
EP 2216356 discloses polymers comprising fluorene repeat units with triphenylamine repeat units pendant from the fluorene units.
Polymers comprising triarylamine repeat units are disclosed in WO 99/54385.
Polymers comprising phenoxazine repeat units are disclosed in WO 2004/060970.